This work was performed to help define the characteristics associated with argon ion lasers which are the most frequently used laser source in animal and human research for intravascular tissue ablation. Argon lasers were studied in air, blood, saline, and saline blood mixtures in an attempt to define the mechanism of tissue ablation and sorrounding thermal difusion characteristics. A uniform methodology was employed including careful ocular michrometry and thermographic analyses utilizing adventitial mechanical thermocouples and fast infra-red surface thermography. We found that argon lasers cause nonuniform large-step explosive vaporization of tissue followed by tissue combustion which is associated with marked radial thermal diffusion. Argon lasers appear to be a disadvantageous source for angioplasty given the lack of precision, marked variability in ablative effects, and widespread thermal diffusion to sorrounding normal tissues.